Typical ones of high-strength aluminum alloys include Al—Cu-based, so-called 2000 series aluminum (Al) alloys referred to as duralumin, super duralumin, etc. The main component of the 2000 aluminum alloys is copper (Cu), and the alloys are reinforced mainly by participation of CuAl2 (θ phase) or a similar phase.
Although strength can be further improved by adding elements, such as Mg, to the Al—Cu alloy, improvement of the strength attained by the addition of such metal elements is limited. In addition, since Al—Cu alloys inherently do not have excellent corrosion resistance, alloy design that further adds alloy element should avoid lowering of corrosion resistance. With Al—Cu binary alloys, uniform structure is unlikely to be obtained, and the freedom in setting the content of Cu is relatively low.
Patent Document 1 (the inventors of this patent and the inventors of the present application overlap) describes that adding carbon (C) in the form of graphite to copper results in higher tensile strength of the resultant Cu—C alloy. In addition, the document also describes a method of preparing such a Cu—C alloy. The present inventors have estimated that if C can be added to an Al—Cu alloy as with the case of Cu, the Al—Cu alloy can be made high in strength.